DocsMessing with the mouse cursor
It it possible to modify the shape of the mouse pointer (also called the X pointer) when in certain states, as we otfen see in programs. For example, a busy application would often display the sand clock over its main window, to give the user a visual hint that he should wait. Let's see how we can change the mouse cursor of our windows.
Creating and destroying a mouse cursor
There are two methods for creating cursors. One of them is by using a set of predefined cursors, that are supplied by the X server, the other is by using a user-supplied bitmap.
In the first method, we use a special font named "cursor", and the function
xcb_create_glyph_cursor:xcb_void_cookie_t xcb_create_glyph_cursor (xcb_connection_t *c, xcb_cursor_t cid, xcb_font_t source_font, /* font for the source glyph */ xcb_font_t mask_font, /* font for the mask glyph or XCB_NONE */ uint16_t source_char, /* character glyph for the source */ uint16_t mask_char, /* character glyph for the mask */ uint16_t fore_red, /* red value for the foreground of the source */ uint16_t fore_green, /* green value for the foreground of the source */ uint16_t fore_blue, /* blue value for the foreground of the source */ uint16_t back_red, /* red value for the background of the source */ uint16_t back_green, /* green value for the background of the source */ uint16_t back_blue) /* blue value for the background of the source */xcb_void_cookie_t xcb_create_glyph_cursor (xcb_connection_t *c, xcb_cursor_t cid, xcb_font_t source_font, /* font for the source glyph */ xcb_font_t mask_font, /* font for the mask glyph or XCB_NONE */ uint16_t source_char, /* character glyph for the source */ uint16_t mask_char, /* character glyph for the mask */ uint16_t fore_red, /* red value for the foreground of the source */ uint16_t fore_green, /* green value for the foreground of the source */ uint16_t fore_blue, /* blue value for the foreground of the source */ uint16_t back_red, /* red value for the background of the source */ uint16_t back_green, /* green value for the background of the source */ uint16_t back_blue) /* blue value for the background of the source */TODO: Describe
source_charandmask_char, for example by giving an example on how to get the values. There is a list there: X Font CursorsSo we first open that font (see Loading a Font) and create the new cursor. As for every X ressource, we have to ask for an X id with
xcb_generate_idfirst:xcb_font_t font; xcb_cursor_t cursor; /* The connection is set */ font = xcb_generate_id (conn); xcb_open_font (conn, font, strlen ("cursor"), "cursor"); cursor = xcb_generate_id (conn); xcb_create_glyph_cursor (conn, cursor, font, font, 58, 58 + 1, 0, 0, 0, 0, 0, 0);xcb_font_t font; xcb_cursor_t cursor; /* The connection is set */ font = xcb_generate_id (conn); xcb_open_font (conn, font, strlen ("cursor"), "cursor"); cursor = xcb_generate_id (conn); xcb_create_glyph_cursor (conn, cursor, font, font, 58, 58 + 1, 0, 0, 0, 0, 0, 0);We have created the cursor "right hand" by specifying 58 to the
source_font argument and 58 + 1 to themask_font.The cursor is destroyed by using the function
xcb_void_cookie_t xcb_free_cursor (xcb_connection_t *c, xcb_cursor_t cursor);xcb_void_cookie_t xcb_free_cursor (xcb_connection_t *c, xcb_cursor_t cursor);In the second method, we create a new cursor by using a pair of pixmaps, with depth of one (that is, two colors pixmaps). One pixmap defines the shape of the cursor, while the other works as a mask, specifying which pixels of the cursor will be actually drawn. The rest of the pixels will be transparent.
TODO: give an example.
Setting a window's mouse cursor
Once the cursor is created, we can modify the cursor of our window by using
xcb_change_window_attributesand using theXCB_CWCURSORattribute:uint32_t mask; uint32_t value_list; /* The connection and window are set */ /* The cursor is already created */ mask = XCB_CWCURSOR; value_list = cursor; xcb_change_window_attributes (conn, window, mask, &value_list);uint32_t mask; uint32_t value_list; /* The connection and window are set */ /* The cursor is already created */ mask = XCB_CWCURSOR; value_list = cursor; xcb_change_window_attributes (conn, window, mask, &value_list);Of course, the cursor and the font must be freed.
Complete example
The following example displays a window with a button. When entering the window, the window cursor is changed to an arrow. When clicking once on the button, the cursor is changed to a hand. When clicking again on the button, the cursor window gets back to the arrow. The Esc key exits the application.
#include <stdlib.h> #include <stdio.h> #include <string.h> #include <xcb/xcb.h> #define WIDTH 300 #define HEIGHT 150 static xcb_gc_t gc_font_get (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, const char *font_name); static void button_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label); static void text_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label); static void cursor_set (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int cursor_id); static void button_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label) { xcb_point_t points[5]; xcb_void_cookie_t cookie_gc; xcb_void_cookie_t cookie_line; xcb_void_cookie_t cookie_text; xcb_generic_error_t *error; xcb_gcontext_t gc; int16_t width; int16_t height; uint8_t length; int16_t inset; length = strlen (label); inset = 2; gc = gc_font_get(c, screen, window, "7x13"); width = 7 * length + 2 * (inset + 1); height = 13 + 2 * (inset + 1); points[0].x = x1; points[0].y = y1; points[1].x = x1 + width; points[1].y = y1; points[2].x = x1 + width; points[2].y = y1 - height; points[3].x = x1; points[3].y = y1 - height; points[4].x = x1; points[4].y = y1; cookie_line = xcb_poly_line_checked (c, XCB_COORD_MODE_ORIGIN, window, gc, 5, points); error = xcb_request_check (c, cookie_line); if (error) { fprintf (stderr, "ERROR: can't draw lines : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_text = xcb_image_text_8_checked (c, length, window, gc, x1 + inset + 1, y1 - inset - 1, label); error = xcb_request_check (c, cookie_text); if (error) { fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_gc = xcb_free_gc (c, gc); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } static void text_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label) { xcb_void_cookie_t cookie_gc; xcb_void_cookie_t cookie_text; xcb_generic_error_t *error; xcb_gcontext_t gc; uint8_t length; length = strlen (label); gc = gc_font_get(c, screen, window, "7x13"); cookie_text = xcb_image_text_8_checked (c, length, window, gc, x1, y1, label); error = xcb_request_check (c, cookie_text); if (error) { fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_gc = xcb_free_gc (c, gc); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } static xcb_gc_t gc_font_get (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, const char *font_name) { uint32_t value_list[3]; xcb_void_cookie_t cookie_font; xcb_void_cookie_t cookie_gc; xcb_generic_error_t *error; xcb_font_t font; xcb_gcontext_t gc; uint32_t mask; font = xcb_generate_id (c); cookie_font = xcb_open_font_checked (c, font, strlen (font_name), font_name); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); xcb_disconnect (c); return -1; } gc = xcb_generate_id (c); mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; value_list[0] = screen->black_pixel; value_list[1] = screen->white_pixel; value_list[2] = font; cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_font = xcb_close_font_checked (c, font); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } return gc; } static void cursor_set (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int cursor_id) { uint32_t values_list[3]; xcb_void_cookie_t cookie_font; xcb_void_cookie_t cookie_gc; xcb_generic_error_t *error; xcb_font_t font; xcb_cursor_t cursor; xcb_gcontext_t gc; uint32_t mask; uint32_t value_list; font = xcb_generate_id (c); cookie_font = xcb_open_font_checked (c, font, strlen ("cursor"), "cursor"); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cursor = xcb_generate_id (c); xcb_create_glyph_cursor (c, cursor, font, font, cursor_id, cursor_id + 1, 0, 0, 0, 0, 0, 0); gc = xcb_generate_id (c); mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; values_list[0] = screen->black_pixel; values_list[1] = screen->white_pixel; values_list[2] = font; cookie_gc = xcb_create_gc_checked (c, gc, window, mask, values_list); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } mask = XCB_CW_CURSOR; value_list = cursor; xcb_change_window_attributes (c, window, mask, &value_list); xcb_free_cursor (c, cursor); cookie_font = xcb_close_font_checked (c, font); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } int main () { xcb_screen_iterator_t screen_iter; xcb_connection_t *c; const xcb_setup_t *setup; xcb_screen_t *screen; xcb_generic_event_t *e; xcb_generic_error_t *error; xcb_void_cookie_t cookie_window; xcb_void_cookie_t cookie_map; xcb_window_t window; uint32_t mask; uint32_t values[2]; int screen_number; uint8_t is_hand = 0; /* getting the connection */ c = xcb_connect (NULL, &screen_number); if (!c) { fprintf (stderr, "ERROR: can't connect to an X server\n"); return -1; } /* getting the current screen */ setup = xcb_get_setup (c); screen = NULL; screen_iter = xcb_setup_roots_iterator (setup); for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter)) if (screen_number == 0) { screen = screen_iter.data; break; } if (!screen) { fprintf (stderr, "ERROR: can't get the current screen\n"); xcb_disconnect (c); return -1; } /* creating the window */ window = xcb_generate_id (c); mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; values[0] = screen->white_pixel; values[1] = XCB_EVENT_MASK_KEY_RELEASE | XCB_EVENT_MASK_BUTTON_PRESS | XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_POINTER_MOTION; cookie_window = xcb_create_window_checked (c, screen->root_depth, window, screen->root, 20, 200, WIDTH, HEIGHT, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, screen->root_visual, mask, values); cookie_map = xcb_map_window_checked (c, window); /* error managing */ error = xcb_request_check (c, cookie_window); if (error) { fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code); xcb_disconnect (c); return -1; } error = xcb_request_check (c, cookie_map); if (error) { fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code); xcb_disconnect (c); return -1; } cursor_set (c, screen, window, 68); xcb_flush(c); while (1) { e = xcb_poll_for_event(c); if (e) { switch (e->response_type & ~0x80) { case XCB_EXPOSE: { char *text; text = "click here to change cursor"; button_draw (c, screen, window, (WIDTH - 7 * strlen(text)) / 2, (HEIGHT - 16) / 2, text); text = "Press ESC key to exit..."; text_draw (c, screen, window, 10, HEIGHT - 10, text); break; } case XCB_BUTTON_PRESS: { xcb_button_press_event_t *ev; int length; ev = (xcb_button_press_event_t *)e; length = strlen ("click here to change cursor"); if ((ev->event_x >= (WIDTH - 7 * length) / 2) && (ev->event_x <= ((WIDTH - 7 * length) / 2 + 7 * length + 6)) && (ev->event_y >= (HEIGHT - 16) / 2 - 19) && (ev->event_y <= ((HEIGHT - 16) / 2))) is_hand = 1 - is_hand; is_hand ? cursor_set (c, screen, window, 58) : cursor_set (c, screen, window, 68); } case XCB_KEY_RELEASE: { xcb_key_release_event_t *ev; ev = (xcb_key_release_event_t *)e; switch (ev->detail) { /* ESC */ case 9: free (e); xcb_disconnect (c); return 0; } } } free (e); } } return 0; }#include <stdlib.h> #include <stdio.h> #include <string.h> #include <xcb/xcb.h> #define WIDTH 300 #define HEIGHT 150 static xcb_gc_t gc_font_get (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, const char *font_name); static void button_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label); static void text_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label); static void cursor_set (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int cursor_id); static void button_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label) { xcb_point_t points[5]; xcb_void_cookie_t cookie_gc; xcb_void_cookie_t cookie_line; xcb_void_cookie_t cookie_text; xcb_generic_error_t *error; xcb_gcontext_t gc; int16_t width; int16_t height; uint8_t length; int16_t inset; length = strlen (label); inset = 2; gc = gc_font_get(c, screen, window, "7x13"); width = 7 * length + 2 * (inset + 1); height = 13 + 2 * (inset + 1); points[0].x = x1; points[0].y = y1; points[1].x = x1 + width; points[1].y = y1; points[2].x = x1 + width; points[2].y = y1 - height; points[3].x = x1; points[3].y = y1 - height; points[4].x = x1; points[4].y = y1; cookie_line = xcb_poly_line_checked (c, XCB_COORD_MODE_ORIGIN, window, gc, 5, points); error = xcb_request_check (c, cookie_line); if (error) { fprintf (stderr, "ERROR: can't draw lines : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_text = xcb_image_text_8_checked (c, length, window, gc, x1 + inset + 1, y1 - inset - 1, label); error = xcb_request_check (c, cookie_text); if (error) { fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_gc = xcb_free_gc (c, gc); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } static void text_draw (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int16_t x1, int16_t y1, const char *label) { xcb_void_cookie_t cookie_gc; xcb_void_cookie_t cookie_text; xcb_generic_error_t *error; xcb_gcontext_t gc; uint8_t length; length = strlen (label); gc = gc_font_get(c, screen, window, "7x13"); cookie_text = xcb_image_text_8_checked (c, length, window, gc, x1, y1, label); error = xcb_request_check (c, cookie_text); if (error) { fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_gc = xcb_free_gc (c, gc); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } static xcb_gc_t gc_font_get (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, const char *font_name) { uint32_t value_list[3]; xcb_void_cookie_t cookie_font; xcb_void_cookie_t cookie_gc; xcb_generic_error_t *error; xcb_font_t font; xcb_gcontext_t gc; uint32_t mask; font = xcb_generate_id (c); cookie_font = xcb_open_font_checked (c, font, strlen (font_name), font_name); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); xcb_disconnect (c); return -1; } gc = xcb_generate_id (c); mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; value_list[0] = screen->black_pixel; value_list[1] = screen->white_pixel; value_list[2] = font; cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cookie_font = xcb_close_font_checked (c, font); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } return gc; } static void cursor_set (xcb_connection_t *c, xcb_screen_t *screen, xcb_window_t window, int cursor_id) { uint32_t values_list[3]; xcb_void_cookie_t cookie_font; xcb_void_cookie_t cookie_gc; xcb_generic_error_t *error; xcb_font_t font; xcb_cursor_t cursor; xcb_gcontext_t gc; uint32_t mask; uint32_t value_list; font = xcb_generate_id (c); cookie_font = xcb_open_font_checked (c, font, strlen ("cursor"), "cursor"); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } cursor = xcb_generate_id (c); xcb_create_glyph_cursor (c, cursor, font, font, cursor_id, cursor_id + 1, 0, 0, 0, 0, 0, 0); gc = xcb_generate_id (c); mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; values_list[0] = screen->black_pixel; values_list[1] = screen->white_pixel; values_list[2] = font; cookie_gc = xcb_create_gc_checked (c, gc, window, mask, values_list); error = xcb_request_check (c, cookie_gc); if (error) { fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } mask = XCB_CW_CURSOR; value_list = cursor; xcb_change_window_attributes (c, window, mask, &value_list); xcb_free_cursor (c, cursor); cookie_font = xcb_close_font_checked (c, font); error = xcb_request_check (c, cookie_font); if (error) { fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); xcb_disconnect (c); exit (-1); } } int main () { xcb_screen_iterator_t screen_iter; xcb_connection_t *c; const xcb_setup_t *setup; xcb_screen_t *screen; xcb_generic_event_t *e; xcb_generic_error_t *error; xcb_void_cookie_t cookie_window; xcb_void_cookie_t cookie_map; xcb_window_t window; uint32_t mask; uint32_t values[2]; int screen_number; uint8_t is_hand = 0; /* getting the connection */ c = xcb_connect (NULL, &screen_number); if (!c) { fprintf (stderr, "ERROR: can't connect to an X server\n"); return -1; } /* getting the current screen */ setup = xcb_get_setup (c); screen = NULL; screen_iter = xcb_setup_roots_iterator (setup); for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter)) if (screen_number == 0) { screen = screen_iter.data; break; } if (!screen) { fprintf (stderr, "ERROR: can't get the current screen\n"); xcb_disconnect (c); return -1; } /* creating the window */ window = xcb_generate_id (c); mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; values[0] = screen->white_pixel; values[1] = XCB_EVENT_MASK_KEY_RELEASE | XCB_EVENT_MASK_BUTTON_PRESS | XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_POINTER_MOTION; cookie_window = xcb_create_window_checked (c, screen->root_depth, window, screen->root, 20, 200, WIDTH, HEIGHT, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, screen->root_visual, mask, values); cookie_map = xcb_map_window_checked (c, window); /* error managing */ error = xcb_request_check (c, cookie_window); if (error) { fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code); xcb_disconnect (c); return -1; } error = xcb_request_check (c, cookie_map); if (error) { fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code); xcb_disconnect (c); return -1; } cursor_set (c, screen, window, 68); xcb_flush(c); while (1) { e = xcb_poll_for_event(c); if (e) { switch (e->response_type & ~0x80) { case XCB_EXPOSE: { char *text; text = "click here to change cursor"; button_draw (c, screen, window, (WIDTH - 7 * strlen(text)) / 2, (HEIGHT - 16) / 2, text); text = "Press ESC key to exit..."; text_draw (c, screen, window, 10, HEIGHT - 10, text); break; } case XCB_BUTTON_PRESS: { xcb_button_press_event_t *ev; int length; ev = (xcb_button_press_event_t *)e; length = strlen ("click here to change cursor"); if ((ev->event_x >= (WIDTH - 7 * length) / 2) && (ev->event_x <= ((WIDTH - 7 * length) / 2 + 7 * length + 6)) && (ev->event_y >= (HEIGHT - 16) / 2 - 19) && (ev->event_y <= ((HEIGHT - 16) / 2))) is_hand = 1 - is_hand; is_hand ? cursor_set (c, screen, window, 58) : cursor_set (c, screen, window, 68); } case XCB_KEY_RELEASE: { xcb_key_release_event_t *ev; ev = (xcb_key_release_event_t *)e; switch (ev->detail) { /* ESC */ case 9: free (e); xcb_disconnect (c); return 0; } } } free (e); } } return 0; }